The invention relates to a hold function for temporarily holding an operationally ready motor vehicle in a stationary state by means of a service brake, which is actuated by electrohydraulic, electropneumatic or electromechanical means.
For enhanced comfort and increased safety of vehicles, there already exist a wide variety of methods and devices that are intended for preventing an operationally ready motor vehicle from starting to roll, but not necessarily for use on slopes. In at least one operating mode of the motor vehicle in the case of an activated brake pedal or an additional operator control element, which is provided for this purpose, the braking force is usually held or actively built-up at least at one wheel of a vehicle. This braking force can also be built up as a function of the degree to which the brake pedal or operator control element is activated.
Such functions and the corresponding devices are known, for example, under the names start-up assistant, hill assistant, hill hold(er), automatic hold or within the framework of speed control systems having an intervehicle spacing function as far as a state of immobilization, all of which are referred to hereinafter in general as the parking brake functions for temporarily holding an operationally ready motor vehicle in a stationary state. These systems that prevent the operationally ready motor vehicle from starting to roll are configured, for example, as (electro) hydraulic or as (electro) pneumatic or optionally also as electromechanical brake systems that can be electronically controlled and which manage to temporarily hold the operationally ready vehicle and to prevent the vehicle from starting to roll.
There also exist methods, in which the vehicle is prevented from starting to roll by means of the transmission (in particular, an automatic transmission).
In addition to these parking brake functions for temporarily holding an operationally ready motor vehicle in a stationary state by way of a service brake that is actuated electrohydraulically, electropneumatically or electromechanically, there also exist (electro) mechanical hold functions, which are intended to permanently hold the vehicle, which is typically parked, in an immobilized state. In this case the brake pressure or rather the braking force (braking torque) for permanently holding the vehicle is maintained by a mechanical device on the hand brake, more particularly, the parking brake. One example of such a hold function or device is, for example, an electromechanical parking brake. Such hold functions, which maintain the brake pressure by a mechanical device in order to permanently hold the vehicle in a stationary state, are not subsumed under the subject matter of the invention.
In order to activate and deactivate the service brake within the framework of the aforementioned electrohydraulic, electropneumatic or electromechanical parking brake functions for temporarily holding an operationally ready motor vehicle in a stationary state, there are a wide range of triggering conditions and/or conditions that must be fulfilled. The requisite auxiliary measures—control signals or switching elements—for representing and/or executing the parking brake functions are, for example, usually one or more speed signals for detecting the stationary state of the vehicle and (electro) pneumatic or (electro) hydraulic actuators in the wheel brakes and/or in the feed lines to the wheel brakes, by which the braking effect can be increased, decreased, and/or can be held temporarily. Optionally, the signals of longitudinal acceleration or inclination sensors, by which the longitudinal inclination of the roadway is determined, and from which the necessary braking force for a guaranteed immobilization of the vehicle and the startup torque, which is necessary for the roadway inclination, can be determined.
Moreover, there may be one or more pressure sensors, by which the brake pressure or rather the generated brake torque at the wheel brake(s) can be determined.
In order to prevent the service brake from being activated within the framework of an above defined parking brake function for temporarily holding the operationally ready motor vehicle in a stationary state, when the vehicle is unsecured, that is, the driver is not sitting in the vehicle, the presence of the driver must be detected and evaluated. Hence, the current BMW X5 vehicles are equipped with a device for detecting the seat occupancy in the form of a seat occupancy mat, by which the presence and/or absence of the driver in the driver's seat can be determined. The parking brake function (automatic hold) for holding the operationally ready motor vehicle by use of the service brake is rendered operationally ready (that is, can be activated or is already activated), if the driver's seat is occupied. This parking brake function is automatically deactivated (if it was already activated beforehand), when no one is detected in the driver's seat while the engine is running. In contrast to this parking brake function for temporarily holding the operationally ready vehicle, the activated electromechanical parking brake for permanently holding the vehicle remains activated, even if the driver has left the vehicle.
Furthermore, DE 10 2005 024 834 B3 also discloses a parking brake function for temporarily holding an operationally ready motor vehicle by use of the service brake. In this case, the driver's presence is detected and evaluated for the purpose of automatically activating the service brake. The driver's presence is determined by use of interior cameras, weight sensors and/or sensors that detect the buckling up of the driver's seat belt. Such engineering measures for detecting the driver's presence can be very expensive under some circumstances. Moreover, the detection of the driver's presence by way of a seat mat can be very slow in part, so that there may be some delay in the detection of the driver's presence and/or absence.
The object of the invention is to provide a parking brake function that is intended for temporarily holding an operationally ready motor vehicle in a stationary state and that detects the driver's presence in the driver's seat in a simple and cost effective manner, and yet guarantees the necessary safety.
This and other objects are achieved by a hold function method for temporarily holding an operationally ready motor vehicle in a stationary state by use of a service brake, which is actuated electrohydraulically, electropneumatically, or electromechanically, wherein the service brake can be activated within the framework of the hold function, when the speed of the vehicle is less than a preset first speed threshold, and the presence of the driver in the driver's seat is detected. The presence of the driver in the driver's seat is detected as a function of the signal of a flap sensor for detecting an opened or closed position of the flap, assigned to the flap sensor.
It is well known from the prior art that within the framework of the aforementioned parking brake functions for temporarily holding an operationally ready motor vehicle in a stationary state, the service brake in operationally ready motor vehicles can be manually or automatically activated while the motor vehicle is at a standstill, if the speed of the motor vehicle is below a preset first speed threshold (that is, the stationary state of the vehicle is detected) and the presence of the driver in the driver's seat is detected. Then a motor vehicle is operationally ready, if, for example, the communications bus system(s) in the vehicle is (are) in operation and/or if at least the ignition is on or the drive unit has been started. The drive unit may be any drive unit, such as an internal combustion engine or an electric motor. The parking brake function may be herein, for example, a start-up assistant, an automatic hold function or a parking brake function within the framework of a speed control system, which is regulated as far as into a stationary state.
At this point the fundamental idea of the invention is to detect the driver's presence with an alternative sensor unit, which is cost effective and responds quickly. Working on this basis, the method according to the invention is characterized by the fact that the presence of the driver in the driver's seat is detected as a function of the signal of a flap sensor for sensing an opened or closed position of the flap that is assigned to the flap sensor. The term “flap” is defined as all flaps that no longer separate the interior of the vehicle from the exterior of the vehicle when the flaps are in the opened position. Thus, this term includes all doors, windows and optionally sun roofs and tailgates. Within the scope of this invention the actuators, which are used for automatically holding the vehicle, when the drive unit and/or the ignition is (are) switched on, include predominantly those actuators that can be actuated by (electro) hydraulic and/or (electro) pneumatic and optionally also (electro) mechanical means and that effect a temporary automatic hold of the service brake while the motor vehicle is running.
In the simplest embodiment of the invention, the presence of the driver in the driver's seat is detected as a function of the signal of the driver's door flap sensor. As an alternative and/or in addition, it is also possible to evaluate other flap sensor signals, because under some circumstances there is the possibility of the driver leaving the vehicle not through the driver's door (because, for example, the locking mechanism is defective or there is no space to open the door), but rather leaving the vehicle through a different vehicle aperture, such as the passenger door, a window or the tailgate.
In order to detect the driver's presence in the driver's seat, the signal of the corresponding flap sensor is evaluated to the effect that the driver's presence in the driver's seat is detected, when the flap sensor, in particular, the driver's door flap sensor, detects a closed position of the flap. Analogous to the aforesaid, the driver's absence can be detected, when the flap sensor detects an unclosed or rather an opened position of the corresponding flap.
The flap sensor can be configured as the door contact switch, which can differentiate between an open or a closed position of the flap. For example, it is also possible to use for safety reasons, instead of a simple door contact switch, an “intrinsically safer” redundancy door contact switch, that is, a door contact switch that can be monitored and/or diagnosed.
As an alternative, the detected driver's presence can be guaranteed by including redundant and/or semi-redundant information about the driver's presence. In addition, the signal from a switch of the driver's seat belt buckle can be evaluated. The activation of the service brake on the basis of the parking brake function would be possible only if both the flap sensor signal and the signal from the switch of the driver's seat belt buckle indicated the presence of the driver in the driver's seat, that is, if a locked driver's seat belt were to be detected.
In another advantageous embodiment of the invention, the presence of the driver can also be detected when a locked driver's seat belt is detected when in a stationary state (that is, at a speed that is less than the preset first speed threshold) the flap is in an open position, detected by the flap sensor, and when advantageously the flap, which is open in the stationary state, was previously closed.
In order to rule out the possibility that the driver has opened a monitored flap for just a short period of time, an advantageous embodiment of the invention provides that the service brake can be activated within the framework of the aforementioned parking brake functions for temporarily holding an operationally ready motor vehicle, only if at least one flap sensor detects a closed position of the flap, assigned to this flap sensor, for a predefined first time interval, for example, of 0.5 seconds.
Similarly, an additional advantageous embodiment of the invention provides that the service brake, which is activated on the basis of the parking brake function, would have to be deactivated manually, only if once again at least one flap sensor detects a closed flap of the flap, assigned to this flap sensor, for a predefined second time interval, for example, of 1.0 seconds.
Advantageously even more conditions have to be satisfied before the parking brake function and/or the service brake, which is to be activated within the framework of the parking brake function, can be activated (automatically). Thus, it is logical, for example, to activate the service brake within the framework of the respective parking brake function only if in addition to the point-in-time of the potential activation, no risk of the vehicle slipping, turning or overturning is detected or expected.
In order to guarantee that the service brake is and/or can be activated only if the driver is sitting in the vehicle and can intervene, if desired, in the control of the vehicle, the driver's presence in the driver's seat even during the time, in which the service brake, which is temporarily activated based on a hold function, must be monitored and evaluated. In this case, too, the driver's presence can be determined as a function of the signal of a corresponding flap sensor for detecting an opened and/or closed position of the flap. Consequently one advantageous embodiment of the invention provides that the service brake, which is activated temporarily on the basis of the parking brake function, can be automatically deactivated again, if the flap sensor for detecting a closed or opened position of the flap, assigned to this flap sensor, detects an open position of the flap, and/or if an existing seat belt sensor at the driver's seat detects an open position of the driver's seat belt. In one advantageous embodiment only the position of the driver's door is monitored.
However, it is also possible to monitor the other flaps, such as the passenger door, the doors in the rear region of the motor vehicle, the windows and/or the tailgate, because the driver could also leave the vehicle through one of the other flap apertures.
Since it can happen that the driver opens the driver's door for just a short period of time, but does not leave the vehicle, an alternative embodiment provides that in the course of evaluating the signal of the flap sensor the automatically activated service brake cannot be automatically deactivated until the flap sensor for detecting the open and/or closed position of the flap, assigned to this flap sensor, detects an open position of the flap for a predefined first time interval and/or not until a defined speed threshold is undershot. This engineering measure guarantees that the service brake is not already deactivated when the driver opens one of the monitored flaps for just a short period of time.
For safety reasons the activated service brake is advantageously also automatically deactivated independently of the signal of the flap sensor, when the drive unit is switched off and/or when the risk of the vehicle turning, slipping or overturning is detected.
Before the service brake is automatically deactivated because of the detected absence of the driver, for safety reasons the surroundings of the vehicle can also be monitored and evaluated, so that the service brake for temporarily holding the vehicle is not automatically deactivated, when, for example, a person is directly in front of or behind the vehicle. In order to be able to detect and/or expect the presence of a person in front of or behind the vehicle, one advantageous embodiment provides that the position of the engine hood and/or the tailgate or, for example, also the signals of parking sensors, parking cameras or the signals of sensors of automatic speed control systems, etc. can also be evaluated.
If, in addition to an opened vehicle door, in particular the driver's door, and thus, the detected absence of the driver, an open engine hood or an open tailgate or, based on other sensor signals, a person is detected in close proximity of the vehicle, then the deactivation of the service brake may be suppressed. This measure can eliminate the risk of endangering a person located in front of and/or behind the vehicle.
If the automatically activated service brake is automatically deactivated due to the detected absence of the driver or any other hazardous situation, a warning signal can be emitted, so that the driver knows that his vehicle is no longer being held, or will no longer be held in a very short period of time, by the service brake that was activated on the basis of the parking brake function. The warning signal should be designed in such a manner that the driver is aware of the warning, even if he is in the process of leaving the vehicle. The warning is advantageously an acoustic and/or optical warning.
As an alternative or in addition, an alternative device for permanently holding the vehicle, for example, an electromechanical parking brake (parking brake), can also be activated. When the drive unit is switched off, this parking brake usually effects a permanent hold of the vehicle. This measure guarantees that the vehicle will continue to be held in a stationary state, even if the driver has left the vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.